The UK Patents Rules 2007 will be corrected as of 1 October 2011 to specify that time periods should be calculated by starting one day after the defining date (the so-called "exclusive rule"). In other words, a period of 1 month "from 15 April" ends on 15 May. Until now there had been some confusion with regard to deadlines with the wording "X days/months/years beginning with" or "beginning on" a particular date or event, which were instead sometimes calculated by starting on the defining date (the so-called "inclusive rule"). This wording has now been changed to substitute "beginning immediately after" for "beginning with", such that time periods are calculated using the exclusive rule. Time periods in the UK Patents Act 1977 itself have not been altered. In particular the 20-year term of a UK patent remains unchanged: "20 years beginning with the date of filing", so should still be calculated using the inclusive rule.